(1) Field of the Invention
The present invention relates to the use of hexanal in vapor form as an antifungal agent for fruits and vegetables. The present invention also provides odor (aroma) enhancement in the fruits and vegetables. This is accomplished by treating the fruit or vegetable for at least 36 hours with the hexanal.
(2) Description of Related Art
Prior art of interest is described in U.S. Pat. No. 4,336,273 to Lee; U.S. Pat. No. 4,387,248 to Pickenhagen; and Caccioni et al., J. Plant Diseases and Protection 102 (5):518-525 (1995)).
Many kinds of synthetic fungicides have been used to prevent decay of perishable plant products, although, some may pose oncogenic risks, which has lead to public concern. As a result, fungicides will face greater restrictions and limitations in the future. Using natural products with fungistatic properties may be an attractive alternative to prevent decay. There is also an ever-increasing demand by the consumer for consistently safe healthy food with good flavor quality. Solving of these major problems is an important step forward, not only for plant production, but also for food science and technology.
Postharvest fungicides and fungistats are used only in a select few commodities. The reason for the lack of chemical use is that residue levels on treated products tend to be quite high relative to fungicides applied pre-harvest. This is primarily due to the short time between application and consumption. In those few instances where postharvest fungicides are applied, they are usually applied as a drench treatment in which the fruit or vegetables are either submerged or a stream of material is applied from above. In some cases, postharvest fungicides are applied in a wax.
Thus, treated products are subjected to a wetting treatment in the prior art. The mix is recirculated numerous times, such that a significant load of dirt, fungal spores and other material are deposited on all of the produce. The application procedure is time-demanding and expensive and interrupts the flow of product into storage.
Loss of perishable fruit and vegetables during the postharvest period is estimated to range from 20% to 25% despite the use of sophisticated postharvest storage facilities and techniques (Jeffries, P., and M. J. Jeger, Postharvest News Info. 5:365-368 (1990); Kelman, A., Phytopathology 1374 (1989)). Of these losses, decay accounts for a significant proportion. Many kinds of synthetic fungicides have been used to prevent the decay of perishable plant products, although some may pose carcinogenic risks, which has led to public concern (Wisniewski, M. E. and C. L. Wilson, HortScience 27:94-98 (1992)). As a result, fungicides will face greater restrictions and limitations in the future. Using natural products with fungistatic properties may be an attractive alternative to prevent decay. Wilson et al (Wilson, C. L., et al., Crop Protection 10:172-177 (1991)) noted that a number of natural volatile compounds have fumigative effects.
Six-carbon (C.sub.6) aldehydes have been found to inhibit the hyphae growth of Alternaria alternata and Botrytis cinerea (Hamilton-Kemp, T. R., et al., J. Chem. Ecol. 18:1083-1091 (1992)). Six-carbon aldehydes, with or without double bonds are dominant compounds released by plant material through the lipoxygenase pathway after tissue damage (Vick, B. A. and D. C. Zimmerman, Oxidative systems for modification of fatty acids: The lipoxygenase pathway, 53-90. In: P. K. Stumpf (ed.). The biochemistry of plants. vol. 9. Academic Press (1987)). It has not been determined if these wound volatiles are involved in the active or passive defense systems in the plant.
Six-carbon aldehydes are also important precursors for the formation of C.sub.6 alcohols and C.sub.6 -containing esters, which are among the most abundant volatile compounds in apple, pears, and bananas and contribute to typical fruity odors (Paillard, N.M.M., Evolution of the capacity of aldehyde production by crushed apple tissues, during an extended storage of fruits, 368-378. In: G. Charalambous (eds.). The shelf life of foods and beverages. Proc. 4th Intl. Flavor Conf. Elsevier Science publishers B. V., Amsterdam (1986); Paillard, N.M.M., The flavor of apples, pears and quinces. In: I. D. Morton and A. J. MaCleod (eds.). Food Flavors. Part C: The flavor of fruits. Elsevier Science publishers B. V., Amsterdam 1-42 (1990)). Headspace treatment with C.sub.6 aldehydes can enhance total aroma production in "Golden Delicious" apple fruit in low O.sub.2 storage (DePooter, H. L., et al., J. Agr. Food Chem. 31:813-818 (1983)). Even immature fruit, for which volatile biosynthesis is extremely low, respond to C.sub.6 aldehyde application with enhanced aroma volatile biosynthesis (Song, J., and F. Bangerth, Acta Hort. 368:150-159 (1994)).